Vessel for meltable heat storage masses

ABSTRACT

A tapered vessel having a horizontal metallic base plate and vertically extending deformable plastic side walls contains a meltable crystalline heat storage mass having a greater density in its solid than liquid states whereby the mass is urged against the base plate by gravity. A first electric heater is disposed adjacent the base plate for melting the mass. A second electric heater of less heat output than the first heater extends vertically along a side wall of the vessel to form a connecting channel to relieve excess pressures in the region between the base plate and the bottom of the mass. The vessel is provided with corrugated heat exchange ribs to dissipate the stored heat to the air.

, Sept. 5, 1972 541 VESSEL FOR MELTABLE HEAT STORAGE MASSES [72]Inventor: Nikolaus Laiug, Hofener Weg 35- 37, 15 7141 Aldingen nearStuttgart, Germany [22] Filed: July 13, 1970 [21] Appl. No.: 54,553

[30] Foreign Application Priority Data July 31, 1969 Austria .,.7381/69[52] US. Cl. ..219/378, 126/400, 219/341, 219/365, 219/530 [51] Int. Cl."F2411 7/00, H051) 1/00 [58] Field of Search ..219/530, 540, 462, 325,326, 219/341, 365, 378, 399; 126/375, 400;

2,000,455 5/1935 Ralston et a] ..2l9/341 3,083,286 3/1963 Swetlitz..219/462 X 3,283,125 11/1966 Snelling....'... ..219/365 FOREIGN PATENTSOR APPLICATIONS 660,030 8/1965 Belgium ..219/378 1,249,776 1 1/1960Primary Examiner-A. Bartis Attorney-Penni'e, Edmonds, Morton, Taylor andAdams plate and verticallyextending deformable plastic side wallscontains a meltable crystalline heat storage mass having a greaterdensity in its solid than liquid states whereby the mass is urgedagainstthe base plate by gravity. A first electric heater is disposed adjacentthe base plate for melting the mass. A second electric heater of lessheat output than the first heater extends vertically along a side wallof the vessel to form a connecting channel to relieve excesspressures inthe region between the base plate and the bottom of the mass. The vesselis provided with corrugated heat exchange ribs to dissipate the storedheat to the air.

5 Claims, 4 Drawing Figures France ..219/34l VESSEL FOR MELTABLE HEATSTORAGE MASSES OBJECTS OF THE INVENTION The melting of solid materialsenclosed in storage vessels, e.g. by means of electrical resistanceheaters, for the purpose of storing latent heat frequently presentsconsiderable difficulties, since the thermal conductivity of most of thecrystalline materials suitable for heat storage is, by comparison withe.g. metals, extremely low even when in the solid state and as a ruleeven considerably worse in the molten state. Consequently elaboratemeasures for the admission of heat by means of metallic ribs or othermeans have to be taken in order to prevent local overheating resultingin vapor pressure or decomposition; their economics'consequently becomequestionable.

Moreover, ifthe melt is lighter than its solid phase, excess pressuresof an almost unlimited magnitude result locally, which cause thesurrounding solid layers to burst; consequently the walls and heatexchange arrangementsv are frequently subjected to extremely highstresses and at the same time considerable noises are caused whichpreclude application to e.g. the heating of dwellings.

DESCRIPTION OF THE INVENTION The invention avoids these disadvantages bymeans of a device in which the crystalline portion of the storage masshas a flat surface which is pressed against the heater. Thereby thecontinuously produced melt, which is no longer capable of absorbing anylatent heat and possesses only low "thermal conductivity, immediatelyflows away, so that direct thermal contact between the heater and thelayer of the crystalline body is permanently maintained. Thereby highspecific heat currents may be applied for melting the material, so thatthe heater itself becomes small and correspondingly cheap.

As a result of giving off its storage heat in the course ofcrystallization, the storage body contracts, so that a cavity is formedin the last region to solidify. When it is remelted, the storage massexpands again to the same degree. In order to avoid local areas ofexcess pressure, the invention provides, at least in the case of storagemasses which contract during solidification, a connection between theregion adjacent the heater and the. said cavity by producing aconnecting channel through which the excess melt flows away without theformation of excess pressures, by means of a second heater. For thepurpose of storage in accordance with the invention it is necessary thatthe core of the store should become released from the walls of thevessel, so that it can describe the vertical movement necessary for themelting process. In accordance with the invention this is accomplishedby means of a tapered construction of the vessel or also by heating thevertical wall of the vessel for short periods, with the aim of melting athin zone adjacent the walls of the vessel and thereby to detach thecore of the store from the wall of the vessel. Electric heaters as wellas heaters with gaseous or liquid heat carriers are suitable forproviding the heating effeet.

If low melting point storage masses are used, the

'storage vessel can be made of heat sensitive materials,

suchas plastics materials. The walls of the vessel may LII also be sothin that they are deformable in a bellowslike manner, as soon asmelting commences.

DESCRIPTION OF THE DRAWINGS Referring to the drawings in which apreferred embodiment of my invention is illustrated:

FIG. 1 shows a broken perspective view of a vessel constructed accordingto the invention; I

FIG. 2 is a section of the vessel of FIG. 1 showing the mass in thesolidified form and also showing the relationship of the vessel withadjacent vessels;

FIG. 3 is a view similar to FIG. 2 showing a portion of the mass insolidified form and in melted form; and

FIG. 4 is a plan view of a portion of FIG. 1.

DETAILED DESCRIPTION OF THE DISCLOSURE v The invention will now beexplained with reference to the drawings.

FIG. 1 shows diagrammatically a storage body for a night storage heater,which comprises a tapered plastic vessel 1 having a top portion 18 wherethe vessel is closed at the bottom by a metallic base. Underneath thebase a resistance heater 2 is provided which together with the base isconnected to the vessel 1 by the bead 6. The supply conductor 3 to theheater also comprises a resistance wire extending over the height of thecontainer and is connected with the vessel 1 in heat conducting. manner.Corrugated aluminum ribs 4 are connected with the walls of adjacentvessels in heat conducting manner and dissipate heat to air which isconducted through them.

FIG. 2 shows a vertical section through a vessel in accordance with FIG.1 in its discharged condition. The interior is charged with a storagemass 10. Since the storage mass, in its solid condition, occupies anappreciably smaller volume than in its liquid condition, a trough 13 isformed in the upper region of the solid body. As soon as the heater 2 isswitched on, the storage mass above the base 11 begins to melt. Sincehowever the supply conductor 3 also develops heat and since it possessesa smaller heat capacity than the heater 2, a strip 12 of melt isproduced along a boundary line of the solid body of storage mass 10, sothat the melt 14 above the base 11 communicates with the upper region 15of the vessel 1. Thereby an excess pressure may be created. In view ofthe higher specific gravity of the storage mass 10, the melt 14 iscompressed into a thin film, so that a very good heat conducting contactis formed between the heater 2 and the body of storage mass 10.

FIG. 3 shows the vessel in its partially charged-up condition. The bodyof storage mass l0 has by now melted to a large extent and is surroundedon all sides by melt. Nevertheless the layer 14 remains extremely thinuntil the body of storage mass 10 has melted in its entirety. The smallamount of heat generated by the supply conductor 3 is transmitted to themolten storage mass 16 by convection. At least those portions of thewall of the vessel not heated by the heaters may be made of a thindeformable plastics material such that the walls will move in abellows-like manner when melting commences; this further assures thatthe solid portion of the storage mass may move vertically within thevessel.

heater for melting the storage mass, a heat exchange arrangement forremoving the heat of crystallization which is produced duringsolidification of the storage mass, and a storage mass having differentdensities in its solid and liquid states; characterized in that saidfirst heater is disposed in a substantially horizontal plane adjacentsaid base plate, that the crystalline portion of the storage mass isurged against the base plate by gravity, and that the verticallyextending walls define a tapered shape, the vessel being wider at itsbase, and having in addition a second heater which extends verticallyfrom the first heater along a portion of the side walls to approximatelythe portion of the vessel opposite said base plate and where said firstheater has a greater thermal output than the second heater. v

2. A storage vessel according to claim 1 characterized in that at leastthe portions of the walls of the vessel which are not heated comprise aplastic material.

3. A storage vessel according to claim 2 characterized in that said baseplate is metallic.

4. A storage vessel according to claim 2 characterized in that theportion of the'side walls that are of a plastic material are deformablewhereby the storage mass when in a solid state can move vertically inthe vessel.

5. A storage vessel according to claim 1 characterized in that said baseplate is metallic.

1. A vessel having a horizontally extending base plate and verticallyextending side walls for containing a meltable heat storage mass, saidvessel having a first heater for melting the storage mass, a heatexchange arrangement for removing the heat of crystallization which isproduced during solidification of the storage mass, and a storage masshaving different densities in its solid and liquid states; characterizedin that said first heater is disposed in a substantially horizontalplane adjacent said base plate, that the crystalline portion of thestorage mass is urged against the base plate by gravity, and that thevertically extending walls define a tapered shape, the vessel beingwider at its base, and having in addition a second heater which extendsvertically from the first heater along a portion of the side walls toapproximately the portion of the vessel opposite said base plate andwhere said first heater has a greater thermal output than the secondheater.
 2. A storage vessel according to claim 1 characterized in thatat least the portions of the walls of the vessel which are not heatedcomprise a plastic material.
 3. A storage vessel according to claim 2characterized in that said base plate is metallic.
 4. A storage vesselaccording to claim 2 characterized in that the portion of the side wallsthat are of a plastic material are deformable whereby the storage masswhen in a solid state can move vertically in the vessel.
 5. A storagevessel according to claim 1 characterized in that said base plate ismetallic.